Method of making coated abrasives



May 15, 1945 N. E. oGLEsBY 1@ 2,375,813

METHOD OF MAKING COATED ABRASIVES Filed June 9, 1941 2 Sheets-Sheet lPPP? mdd

May l5 945 N. E. oGLEsBY METHD OF MAKING COATED ABRASIVES Filed June 9,1941 2 Sheets-Sheet 2 lnverzor ?atente May l5, 1945 METHOD F MAKENGCOATED ABRASIVES Nicholas E. Oglesby, Troy, N. Y., assignor to Behr- IManning Corporation, Troy, N. Y., a corporation of MassachusettsApplication June 9, 1941, Serial No. 397,299

11 Claims.

This invention relates to improvements in the art of making coatedabrasives and particularly to the step of sizing coated abrasives. Theinvention relates among other things, to a method of treating a sizedcoated abrasive with an atmosphere containing a vapor of a solvent forthe adhesive subsequent to the sizing operation.

The present method is particularly adapted to sizing on the abrasivelycoated side, webs of paper, cloth, combinations of cloth and paper orvulcanized fibre and the like to which have been adhesively attached,coats of abrasive grains preferably suitably oriented and to maintainingthe desirable orientation brought about in the step of depositing theabrasive grains. The present invention not only makes it possible tomaintain the grains in substantially their initially applied positionsbut also may be operated to improve the orientation or location ofgrains sometimes brought about in the coating operation, particularlywhere the coating method is not one that gives the optimum orientation,sharpness or roughness desired. Furthermore, the method is not onlyapplicable to the ner grits but is highly desirable in the, case of verycoarse grits where the problem of imparting the desired orientation tothe gritsat the time of thev deposition in the coating step, and theretaining of this orientation has been a problem.

It is an important object of this invention to retain during the sizingoperation the orientation of abrasive grains brought about in thesocalled electrostatic coating methods. It is a further object of thisinvention to produce high grade coated abrasives with optimum roughnessand sharpness. It is a further object of this invention to producecoated abrasives in Awhich the sizing adhesive has been removed from theedges and points of the abrasive grains that engage the work in acommercial abrading operation. It is a still further object of thisinvention to produce oriented coatings of coarse abrasive grains whichare of such a coarseness that they are not readily oriented anddeposited by electrostatic means and subsequently retained in theirdeposited positions. It is still another object of this invention toproduce a superior bond between the abrasive grains and the sizing coatof adhesive as well as between the sizing coa-t of adhesive and thepreviously applied making coat of adhesive. It is a further object ofthis invention to drop, i. e., move the sizing coat of adhesive wellbelow the tops of the abrasive grains and to eliminate a large part ofthe entrapped air bubbles and iilms incident to the application of thesizing coat of adhesive by conventional means.

I am aware of the fact that attempts have been made to make sharp coatedabrasives with upstanding grains, the outermost edges and points ofwhich are free from excessive adhesive, by spray sizing methods, inwhich the sizing adhesive is blown into and among the grains with apropelling charge comprising a Warm solventy vapor-laden gas. I amfurthermore aware that attempts have been made to solve this problem byfirst applying the sizing coat of adhesive in the conventional mannerand then blowing the same down into the grains with a jet of highvelocity solvent-laden gas. I am also aware that it has been proposed toapply an excess of a thin sizing coat of adhesive and then immediately,while the same is uid, blow oi the excess of adhesive, clear the edgesof the grain of adhesive and drop the sizing coat well down among thegrains by means of a high velocity jet of solvent-laden gas. I find,however, that none of these methods serve my purpose in that a jet ofsolvent vapor or warm gas laden with solvent vapor moves the grains fromtheir initially applied positions and produces a relatively at and dullcoat as compared with the product of this invention. This isparticularly true where the making coat of adhesive, as for instanceglue or incompletely cured synthetic resin, is softenable by the sizingcoat. In my process I, thereforeavoid the use of a jet of solvent orsolvent-laden gas impinging against the abrasive coat and thereby avoidthe dulling of the sheet and upsetting of grains incident to suchoperations.

I also iind that if the newly sized coated abra sive as made byconventional methods, as for instance glue bonded coated abrasives orcoated abrasives made with a synthetic resin bond, the making coat ofwhich has, not been rendered completely insoluble in the/sizing coat, issubjected for a considerable period of time, i. e., a time sufiicient tofully accomplish my purpose, to a Warm solvent vapor or a Warmatmosphere containing solvent vapor even without any jet effect,

uct so brought about by subjecting the sized web to an atmosphereconsisting of warm solvent vapor or containing a substantial amountthereof. while the coated abrasive web is traveling horizontally withthe abrasive surface facing downwardly or while the abrasive surface isfacing l downwardly and the direction of travel of the web is at arelatively small angle to the horizon-v tal, as for instance, an angleof about 30 or less. Substantially the horizontal position during thetime of ltreatment is generally preferred. I therefore size myabrasively coated web previously made by any known method, by anyconventional sizing method such as, for instance, calender rolls orsuitable spray means and then quickly, i. e., before serious loss ofgrain orientation occurs, turn the web so that it is traveling with theabrasively coated side facing downwardly and horizontally or, at a smallangle to the horizontal and complete my process with the web travelingin this position. This is a preferred method. Another method will bedescribed later.

After the sized web has been turned so that it travels with the abrasiveside down in a direction parallel to the horizontal or at a small analeto the horizontal, I apply to the web a iluidizing treatment of warmsolvent vapor or a treatment with a warm atmosphere containing asubstantial amountA of solvent vapor such as suffices to preventhardening of the sizing adhesive by the heat during this part of thetreatment. Subseouent io thistreatment of the web, the web continues insubstantially a horizontal direction after emerging from the treatingzone until the adhesive has set up sufficiently to prevent loss oforientation of the abrasize grains, referring of course to orientationbrought about in the deposition of tbe grains and also to such favorableorientation as is further imparted by my special treatment, suchfavorable orientation as is imparted in my treatment being aided in somecases by a beater or vibrator as hereinafter described.

It is a new and unexpected result of my invention that even though afiuidizinar treatment is applied to maintain the fluidity of and evenin-.

crease the fluidity of the sizing adhesive with the abrasive coat facingdownwardly,l nevertheless. the sizing adhesive is cleared off of theabrasive edges and points and travels upwardly to sink deeper into theabrasive grains counter to the force of gravity. I believe that thisphenomenon is a resultant of the actions of capillary and surfacetension forces. Furthermore, even with a glue bond sandpaper product inwhich the glue is readily softenable by the sizing adhesive. in mvtreatment the grains do not drop out of the adhesive coating or moveawayD from the backing to any undesirable extent. Furthermore. since theabrasive is facing downwardly the action of gravity is to maintain thegrains in their upright positions or to bring them into uprightpositions rather than to bring about loss of orientation.

Furthermore, with the adhesive coats in a softened condition. there is arandom displacement of the ends adjacent the backing, conducive to theformation of a close coat abrasive having certain advantages heretoforeenjoyed by open coatings in that the exposed ends of the grains with thegreatest displacement from the backing protrude above those of equalsize having a smaller displacement and engage the work first, the effectof which is a greater pressure on the smaller number of grains untiltheir points have been worn or broken away, so that the points of grainsat a slightly lower level then engage the work.

It is characteristic of the products produced by the preferred methodsof my invention that the exposed points and edges of the abrasive grainsare relatively free from any deleterious quantity of the sizingadhesive; that the coatings are of great depth for the quantity, shapeand size of abrasive grains used and that the exposed ends of the grainsin the top of the coating are spaced far apart and open as compared withconventional coatings carrying the same weight of the same size andshape of abrasize grains. Electrostatic methods of applying abrasivegrains are known in the art which orient substantially all of theabrasive grains with their long axes at right angles to the plane of thebacking in the grainapplying step. Such electrostatic methodsconveniently apply a single layer of grains, one grain deep, withsubstantially all of the grains as initially applied being oriented withtheir long axes substantially at right angles to the plane of thebacking. In a preferred method of carrying out the present invention Iapply a sizing coat of adhesive which will soften the making coat ofadhesive over the abrasive grains so oriented and immediately furthertreat the coated abrasive so sized while the abrasive grains are facingdownwardly to further soften the making coat and render highly fluid thesizing coat and with the coated abrasive in such condition I vibrate it,as, for instance, as illustrated in Figure 1, so as to create a randomdisplacement of the ends of the abrasive grains adjacent the backingfrom their initially applied positions and away from the backing butwithin the making coat of adhesive. After this treatment the adhesivesare set at least sufficiently to support the grains while the abrasivegrains are still facing downwardly. In the resulting product theabrasive grains are still oriented with their long axes substantiallyperpendicular to the backing but as a result of my special treatmenthave their exposed ends extending a correspondingly variable distanceabove the average level of the sizing adhesive, the exposed points andedges of the grains being free from any deleterious quantity of sizingadhesive and the coating being of great depth for the quantity, shapeand size of abrasive grains used and the exposed ends of the grains inthe top of the coating being spaced far apart and open as compared withconventional coatings carrying the same weight and the same size andshape of abrasive grains.

In connection with the treatment just described, I find a beater orvibrator applied to the back of the weby before, concurrently with, orsubsequent,b to the previously described treatment, an aid tomaintaining favorable orientationof the abrasive grains and in manyinstances and undei certain conditions of operation a method and devicethat can further impart to the abrasive grains in the coating morefavorable orientation even thanthat which is present after thedeposition of the abrasive grains but before sizing. This isparticularly true where the preferred electrostatic methods have notbeen used or have been used with such abrasive grains that the maximumorillenting effect cannot be obtained. Furthermore.

this use of a beater or vibrator as a part of my process greatlyimproves abrasive coats made by other than the orienting methods.

It is to be understood that I treat my webs in such a position that thetorques on the individual grains brought about by gravity serve to holdgrains oriented substantially perpendicularly to the backing inposition, or to pull inclined grains into a position perpendicular tothe backing at a time that the adhesive coats are relatively soft andwould not maintain the grains in fixed positions against the forces ofgravity, and thus avoid loss of orientation that has heretoforeoccurred. When in the specification and claims it is stated thatabrasive grains are oriented, it is meant that the grains have theirlong axes substantially at right angles to the plane of the backing. By

stating that the grains have their long axes substantially at rightangles to the plane of the backing, substantially perpendicular to thebacking or substantially normal to the backing, it is meant that thelong axes of the grains approach the right angle, perpendicular ornormal relation to the plane of the backing sufciently close to give thesharpness of coating and abrading efciency associated with orientedcoated abrasives.

Otherwise stated, I treat the web with the abrasive coat facingdownwardly whereby the grains are lightly held at their bases by themaking coat of adhesive and are pendant from the reinforcing backing.

Referring to the drawings,

Figure 1 is a diagrammatic view of a preferred form of this inventionshowing an apparatus and a method that have been found highlysatisfactory.

Figure 2 is a diagrammatic view of still another form of my inventionwhich is sometimes more readily adapted to existing sandpaper machines,wherein the apparatus shown in Figure 1 can be less readily installed.

Referring to Figure 1 I0 is an abrasively coated web which may bedelivered as shown from any commercial sandpaper making machine in theform of conventional festoons supported by travelling slats II and madeto pass over idler rolls I2 to take the web out of festoon form anddeliver it as a traveling web to pass over additional idler rolls I3 andthrough conventional calender rolls I4, the bottom roll of which dipsinto a glue box I5 lilled with a suit- .able adhesive according to thenature of the web I 0 and which may often be animal glue or syntheticresin. In passing through the calender rolls tbe abrasively coated sideof the web I0 has applied thereto a suitable quantity of the sizingadhesive such -as glue; the web then passes quickly and through a shortspace as shown over idler rolls I6 and I'I so that the abrasively coatedside of the web is faced downwardly quickly after sizing whereby toprevent loss of orientation of the abrasive grains which otherwiseaccompanies softening ofthe bottom or make coat of adhesive by thesizing coat of adhesive. Idler roll Il also serves as one damper rollfor certain locations of the whipper, beater or vibrator hereafterreferred to. After the-web has been faced downwardly and beyond idlerroll II, I provide a uidizing chamber I8 with 4slots I9 and 2IJ throughwhich the web enters and leaves the chamber. In this chamber the sizingcoat is maintained fluid or its fluidity is increased and the makingcoat is softened. I also supply -an atmosphere-controlling means 2lwhich may be a pipe of suitable size with a valve 22 which may be openedto any desired degree to admit a controlled quantity of warm solventvapor or a gas laden with solvent vapor. The chamber is preferablyprovided with a perforated plate 23 which further insures uniformdistribution of the con'- ditioning atmosphere and the avoidance of a Kplained is objectionable.

substantial jet effect which as previously ex- In the presentconstruction, the conditioning atmosphere is discharged through aplurality of openings24 in the pipe 2l and thenpasses through theperforated plate so that objectionablejetting action is eliminated. Imay also provide within the chamber, though I usually do not find itnecessary, an independent heating means whereby the temperature withinthe chamber may be subject to control independently of the temperatureof the aforementioned atmosphere-controlling vapors or vapors and gasesintroduced through the supply line 2l into the chamber I8. However, Iusually find it preferable to control the temperature and partialpressure of the atmosphere within the chamber I8 by controlling thequantity and the temperature of vapor or vapor-laden gases that areintroduced through the supply line 2|. In this connection I frequentlyfind a conventional super-heater (not shown) desirable since such asuperheater can be used to control the temperature of the material addedthrough supply line 2| independently of the quantity added which issubject to control by the setting of valve' 22. After the web leaves thechamber I8, it passes over a damper roll 25 and then over a power drivenbeater, or other type of vibrator 26. To bring about the vibrating orbeating action that I desire, I find a power driven hexagonal bar withdimensions of 11/2" between the opposite parallel faces highlysatisfactory. This beater or vibrator is driven at speeds which amongother things depend upon the weight of the backing and the size of theabrasive grains. The web I0 then passes from the power driven beater orvibrator 26 to a damper roll 2'I and thence over an idler roll 2 8 to asuction drum 29 and over additional idler rolls 30 to a conventionalsuction drum and rattler (not shown) where it is picked up by suitableslats to form the customary festoons that are passed to `con ventionalsandpaper drying rooms. The location of the beater or vibrator has beenshown between idler rolls 25 and 21 outside of the treating chamber I8.However, the power driven beater or vibrator 26 may be placed at otherlocations, as for instance, within the chamber I8 and between damperrolls II and 25,

Referring to Figure 2, I0 is the web of unsized 'abrasively coatedcoated abrasive which may be delivered to the apparatus from anycommercial sandpaper making machine in the form of conventional festoonsas illustrated in Figure 1 wherein the traveling festoons are supportedby slats I I and made to pass over idler rolls I2 to take the web out offestoon form and deliver it as a traveling web to pass over idler rollssuch as the idler rolls I3 of Figure 2. It will be appreciated that inthe case of the festoons shown in front of the machine in Figure 1 thefestoons may be moved around a turn to come inside cf the verticalportion of the web l0 between idler roll 28 -and suction drum 29 inFigure 1 The same or similar means may. of course, be

`employed in the case of Figure 2.

The unsized abrasively coated web of Figure 2 is delivered as shown topass over idler rolls I3 and between calender rolls I, the bottom rollof which dips into adhesive in a glue box I5. whereby a suitable sizingcoat is applied over the coat of abrasive grains after which the sizedweb I0 passes over idler rolls 3I, damper roll 32, vibrator or beater33, damper roll 3l, idler roll 35, thence through a uidizing chamber I 8with the abrasively coated side facing downwardly and laden gas may beintroduced into the chamber I8 through ports 24 to maintain or improvefluidity of the sizing coat and soften the making coat. Also, I providea valve-22 which may be us'e'd to control the quantity of conditioningvapor or conditioning vapor-laden gases admitted to the' chamber I8, theperforated plate 23 in the chamber and slots I8 and 20 by which the webI may enter and leave the chamber. After leaving the chamber the web I0passes over damper roll 36, past a driven beater or vibrator 3 1 over adamper roll 38, thence along a substantially horizontal direction or ata predetermined angle-to the horizontal, as indicated, for a distance ortime suflicient for the adhesive to set up and firmly anchor the grainsin place before the sized web, is changed in direction as indicated at28 in Figure 1, and moved to a commercial sandpaper drying room wherethe adhesive is completely dried or cured, as the case may be, dependingupon the nature of the adhesive used. By using apparatus such as thatillustrated in Figure 2, in which the sized web may not always be faceddownwardly before the sizing coat of adhesive has time to substantiallysoften the bottom coat of adhesive, I find that a beater or vibrator maybe used to advantage to minirnize the turning over of the grains,agglomeration of the grains and general loss of orientation before theabrasively coated web is turned over and"faced downwardly in whichposition, as explained before, such loss of orientation is substantiallyminimized or substantially prevented. I furthermore find that a vibratorin any of the positions shown serves an added function of helping toremove entrapped air fllms or bubbles and thereby is conducive to theformation of a superior bond.

Where a beater or vibrator has been shown in Figures 1 and 2, as forinstance, beater or vibrator 23 of Figure 1, whipper or vibrator 33 ofFigure 2 or whipper or vibrator 31 of Figure 2 the whipper or vibratorin question is shown operating between two damper rolls as for instance,damper rolls 25 and 21 of Figure 1, damper rolls 32 and 34 of Figure 2.or damper rolls 36 and 38 of Figure 2. The ideal distance between thesevarious pairs of damper rolls varies somewhat with the weight of thebacking, the weight of adhesive used, and the weight and even the sizeof the abrasive grains, The spacings of these damper rolls for idealoperating conditions may be varied in accordance with the naturalfrequency of vibration of the web upon which the vibrator or whipper isused. However, 130 lb. cylinder paper is a common backing for'manyimportant coated abrasives and using this backing and hide glues, as isstomary in the coated abrasive art, to anchor g ts to the backing, formany coated abrasive articles I find a suitable spacing between theFurthermore, I find that the frequency of vibra tion preferably shouldalso be varied in accordance with the nature and weight of the backing,the weight of adhesive, and the weight and size of abrasive grains used.However, for a large class of products just described made with 130 lb.cylinder paper as a backing, I find that my preferred hexagonal barvibrator heretofore dedamper rolls to be 3'1 inches.y

scribed gives good results if rotated against the backing at a speedwithin the range of 2185 to 4300 revolutions per minute. Specificillustrations of preferred speeds within this range will be given indetailed examples later herein described. Referring to both Figures 1and 2 it will'be noted that the beaters or vibrators 26 of Figure 1 and33 and 31 of Figure 2 have noil been located in the center of the spanbetween the damper rolls adjacent the beater or vibrator in question.The spacings illustrated in Figures l and 2 are such that the point ofcontact of the vibrator or beater with the back of the coated abrasiveweb is 9" fromY one adjacent damper roll and 28" from the other adjacentdamper roll. This spacing has been found to give good results. Itshould, however, be appreciated that many spacings and locationsof thedamper rolls and beaters or vibrators will serve my purpose, includingspacings in which the vibrator is mid- Way between the adjacent damperrolls.

In the operation of the beaters or vibrators, they are made to pressagainst the back of the coated abrasive webs with different forces anddifferent displacements of the web from a straight line between theadjacent damper roll according to the nature of the coated abrasivebeing made. In general, the heavier the backing and/or the coarserV thegrit being coated the more firmly should the vibrator or beater pressagainst the backing. As a result of this pressure of the vibrator orbeater there is a slight deflection in the web so that at the point ofcontact of the beater with the backing the web may, for example, bedeflected from the straight line drawn between the tops of the adjacentdamper rolls within the range of about one-eighth to about iiVe-eighthsof an inch, the smaller deflection normally being used for the lighterbackings and finer grits and the larger deflection for the heavierbackings and coarser grits. It will, thereforel be seen that the damperrolls, or the beater or vibrator, or both the damper rolls and thebeater or vibrator are adjustable, whereby the pressure of the vibratoror beater against the back side of the web may be varied according tothe product being made.

In operating the treating chamber I8 of Figure 1 and similarly thetreating chamber I8 of Figure 2, which, since the operation of the twochambers is similar, I will generally explain by reference to thechamber I8 of Figure l, conditions are created Within the chamber, asfor instance, chamber I8 of Figure l in which there is sufficientsolvent vapor to prevent substantial or rapid evaporation of residualsolvent in the sizing coat of adhesive where such is present, orin anyevent to aid in maintaining a fluid condition of the sizing adhesivewithin the chamber I8. Furthermore, the temperature within the lchamberI8 is controlled to produce and maintain a highly fluid condition in thesizing coat of adhesive without iiuidifying the bottom or making coat ofadhesive to an extent that the abrasive grains would drop therefrom.This is readily accomplished even in the case of standpaper made with ahide glue, and I believe that this is true for several reasons. In therst place, the heat within the treating chamber contacts the surface ofthe sizing coat of adhesive but requires some time to penetrate to thebottom or the making coat of adhesive. Furthermore, the making coat ofadhesive usually contains a higher percentage of glue, for instance,than the sizing coat of adhesive and experience shows that a glue laiddown from a high concentration of solution absorbs water more slowlythan a glue `film laidI down from a lower concentration of solution.There is thus a pronounced delay in the equilibrium distribution of thewater applied in the sizing coat of adhesive between the sizing coat andthe making coat. At any rate, I have found it a practical matter tocreate in the chamber I8. sizing glues not only fully as fluid as thesizing glue at the time of application but, where desired, sizing gluesof much greater fluidity than the fluidity at the time of applicationwhereby the sizing glue actually travels upwardly among the grains toproduce a sharp coated abrasive in which the edges and points of thegrains are remarkably freefrom adhesive, while at the same time avoidingany objectionable movement of the abrasive grains downwardly and awayfrom the backing. By using the treating apparatus and process shown inFigure 1 without the driven beater or vibrator, such as the beater orvibrator 26, I am able to obtain highly desirable results. However, apreferred method of operation is the conjoint use of the treatingchamber and beater or vibrator, especially since the beater or vibratorstraightens up grains which may not have been previously well orientedor which may have st some of their orientation, and also serves toseparate grains that may have become agglomerated or bunched.

Similarly, referring to Figure 2, the treating chamber, in the absenceof either beaters or vibrators 33 or 31, gives desirable results butmaximum sharpness is obtained by the use of either beater or vibrator 33or'beater or vibrator 31 and a preferred method with the apparatus ofFigure 2 is one in which beater or vibrator 33, the treating chamber I8,and beater or vibrator 31 are used. Even with the web in a substantiallyhorizontal position and facing upwardly as between damper rolls 32 and34 in Figure 2, driven beaters or vibrators such as illustrated by 33materially retards loss of orientation which might otherwise occur whereit is impracticable to avoid very substantial travel of the web beforethe abrasive side is faced downwardly.

The various beaters or vibrators shown in Figures 1 and 2 have adesirable eiect in most in stances (depending upon the degree ofsoftening of the making coat of glue by the sizing coat) even in theabsence of the treatment carried out in chamber I8. but the optimumeffect from the vibrators will be obtained where it is used with thesizing coat of adhesive in a condition of optimum fluidity such as thecondition brought about by the treatment in chamber I8 of Figures 1 and2 with the abrasive facing downwardly.

In some cases, the reversal of the position of the abrasively coated webto face the abrasive side downwardly takes place before there has beenany opportunity for the sizing coat to set, while in other cases thesetting or jelling has already been initiated. Where initiation of setof the sizing coat has occurred, the sizing coat may, of course, beuidified in my treating chamber. In any event, it is to be observed thatquickly after sizing the web is disposed so that the oriented grainsproject downwardly.

From the foregoing, it will be appreciated that where the grains areinclined with respect to the perpendicular, they may be caused tolassume a desired perpendicularity and, at the same time, theperpendicularity of abrasive grains existing at that time is maintained.Generally, i. e., for most purposes, it is desired that the grains on acoated abrasive product be oriented with their 'I lmay use other typesof vi-brators such as the well known electromagnetic vibrators tovibrate the web. The frequency and amplitude of vibration may, as in thecase of the hexagonal bar or other form of vibrator, be adjusted inaccordance with the nature of the material being coated.

Specific .examples of the operation of my apparatus and method will nowbe described:

Coated abrasive, Eample 1 This is what is generally known as a ne gritsandpaper. A suitable backing is lb. rope' cylinder paper. A suitablegrit is #400 silicon carbide. A suitable making coat of adhesive is 29%145 millipoise hide glue at a temperature of F., while a suitable sizingsolution is 16% of 86 millipoise hide glue at a temperature of F. Asuitable coating method is any one of the well known and establishedelectrostatic methods such as those described in the Smyser and variousSchacht Patents Nos. 1,788,600, Re.

20,660, and 2,027,309. Using a coating process, backing, adhesive andabrasive grain such as described, I may coat approximately 2.4 lbs. persandpaper ream ofabrasive grains onto the backing by methods -well knownin the art and pass the same to the usual festoons between the mak ingand sizing machines where the making coat of adhesive is given at leastappreciable drying to set up and solidify the making coat of adhesiveand anchor the grains in place. From the festoons the abrasively coatedvweb is passed over idler rolls I2, preferably rubber covered, asillustrated by the web I0 in Figure 1 and thence lby the idler rollspreviously described between the calender rolls I4, where the sizingcoat of adhesive previously mentioned and held at a temperature of 160F. in the glue box I5 is applied over the abrasive grains insubstantially the usual quantity used in commercial practice. From thecalender rolls I4, the sized abrasive web I0 is quickly turned aboutidler rolls I6 and I1 to face the abrasive side downwardly, and with theabra'- sive facing downwardly the web is led through the treatingchamber I8, entering the chamber at slot I9 and leaving it at slot 20.Within the chamber I8 the web is subjected to a. steaming treatment,steam being the vapor of water and water also being the solvent used inmaking the hide glue solution. Steam is admitted through the supply line2l in controlled quantities by adjusting the valve 22 and comes from asuitable source of steam which, in this case, may be steam at 15 lbs.pressure produced from steam in a line at 90 lbs. by a suitable reducingvalve. Since the steam chamber is :below the abrasive web,1i. e.,

the steam is admitted beneath the web and since a jet effect is avoidedin releasing the steam, wet steam will often serve my purpose and ycan.be used without any objectionable condensation on the web. However, Isometimes prefer to use superheated steam, especially as an independentmeans of temperature control. Within the chamber I8, the fluidity of thesizing glue is controlled and increased as desired, but in any event, a

, highly uid condition of the sizing glue is brought racks. Between theemergence of the web from the slot 20 and its turn from the controlleddirection of travel with the abrasive sidefacing downwardly into avertical direction to approach the suction drum 29, the adhesive sets toan extent that loss of orientation or dislocation of the grains afterthe lweb is turned from its controlled position of travel is avoided. Inthis variation of my process, the driven vibrator or whipper, such asthat illustrated by 26, has not Ibeen used but a superior result hasbeen obtained as compared with the coated webs of the prior art.However, a preferred methodof operation includes the driven whipper orbeater 26 which, in this case, may be so set against the backing of theweb that at the point of contact between the whipper and the web the webis displaced about one-eighth of an inch from the straight line drawnbetween the bottoms of damper rolls 25 and 21. Furthermore, a suitablespeed of the whipper in this case is about 3700 revolutions per minute.This is a case in which a relatively heavy backing is combined with arelatively fine grit.

The speed of the traveling web and the size of the chamber I8'in thiscase may be so adjusted that the web is within the chamber for a time ofabout two and one-half to three seconds. The temperature within thechamber may be approximately 140 F. and the quantity of steam added tothe chamber is such as to prevent substantial evaporation of the solventwithin the chamber. Furthermore, the time of travel with the abrasivefacing downwardly after emergence Ifrom the chamber I8 is, in this case,not less than about eight seconds. It will be appreciated that largerchambers and greater distances of travel may be used and that the sizeof the treating chamber may be varied within wide limits. However, it isusually economical of space to use the smallest chamber which will givethe desired effect and the shortest distance of travel which will permitsuiloient setting up of the adhesive to prevent loss of orientation ofthe grains.

Coated abrasive, Example 2 This is what is generally known as a mediumgrit sandpaper. .A suitable backing is 130 lbs. rope cylinder paper. Asuitable grit is #80 fused aluminum oxide abrasive grains. A suitablemaking coat of adhesive is a 46% solution of 86 millipoise hide glue,and a suitable temperature for the application of this adhesive is ,160F. A suitable 4sizing solution is a 31% solution of 86 millipoise hideglue and a suitable temperaturel for the application of the sizing coatof adhesive is 155a F. A suitable coating method for applying theabrasive grains is any one of the well known and establishedelectrostatic methods such as those described in the previouslymentioned Smyser and Schacht patents. Using a coating process, backing,adhesive and abrasive grain such as described, I may coat approximately21.6 lbs. per sandpaper ream of the abrasive grains onto the adhesivelycoated backing. As in the case of Coated abrasive, Example 1, I pass theabrasively coated web to the usual festoons between the making andsizing machines where the making coat of adhesive is given at least anappreciable drying to set up the making coat of adhesive and anchor thegrains in place. The festoons are then taken down continuously aspreviously described and the abrasively coated web is passed through thesizing machine as in the case of Coated abrasive, Example l, wheresubstantially the usual commercial sizing coat of adhesive is appliedover the abrasive grains. From the calender rolls I4, the sized abrasiveweb IU is quickly turned about idler rolls I6 and l1 to face theabrasive side downwardly, and with the abrasive facing downwardly, theweb is led through the treating chamber I8, entering the chamber throughslot I9 and leaving it from slot 20. Within the chamber I8 as in thecase of Coated abrasive, Example 1, the web is subjected to a steamingtreatment and in this case, the temperature within the chamber I8 may beabout Y' 160 F. A highly duid condition of the sizing glue is broughtabout and/or maintained within the chamber I8. Upon emerging -from slot20 of the chamber I8, the web may be passed over roll 26, roll 21, roll28 and the suction drum 28 and thence to the drying racks. Before theweb turns upwardly at roll 28, the adhesive is set to an extent thatloss of orientation or dislocation of the grains after the web is turnedfrom the controlled position of travel is substantially avoided.Alternately, I subjectl the web to the action of a driven vibrator orbeater such as that illustrated by 26, and preferably I subject the webto both the treatment in the chamber I8. before described, and theaction of the driven vibrator or beater 26. With this grit and thisbacking, a desirable speed of the preferred hexagonal vibrator shown is3400 to 3600 revolutions per minute. The time of travel with theabrasive facing downwardly to permit the adhesive to set after thetreatment in the chamber I8 is about eight seconds or more.

With this grit and this backing the hexagonal vibrator 26 may be set topress against the backing with a force which causes a three-eighths ofan inch displacement of the backing at the point of contact with thevibrator from a straight line drawn between the two surfaces of theadjacent damper rolls at their points of contact with the backing.

Coated abrasive, Example 3 tion of 86 millipoise hide glue 'and asuitable temperature for the application of this adhesive is 160 F. Asuitable sizing solution of adhesive for this grit is a 38% solution of86 millipoise hide glue which may -be applied to the abrasively coatedweb at a temperature of F.

As in former examples, a suitable weight of abrasive grains may becoated onto the backing with the making coat of adhesive described andby any of the established methods. In making this grit, I coat onto theadhesively coated back ing about 58 lbs. per sandpaper ream of #30silicon carbide abrasive grains after which the abrasively coated web isgiven substantial drying in -festoon form between the making and sizingmachine and then passed to the sizing machine as illustrated, forexample, diagrammatically in Figure 2.

Referring to Figure 2, the sized abrasive web IIJ then passes over idlerroll 3|, damper roll 32, the beater or vibrator 33, idler rolls 3| and35 after which, without any treatment in chamber I8, the web may bepassed over rolls 36 and 38 and after the adhesive has beenset with theabrasive facing downwardly, it may be passed over rolls and a suctiondrum (not shown) to deliver it to conventional sandpaper drying racks.An improvement will be noted in the abrasively coated web as comparedwith the web similarly made, but without the use of the vibrator 33.Alternately, I may pass the web from vibrator 33 over rolls 34,35 and 36to the action of vibrator 31 without applying a treatment in the chamberI8, and it will be found that there is a further improvement over theweb made in which only the vibrator 33 was used. However, I preferablypass the web from the action of beater 33 over the rolls 34 and 35 intothe treating chamber I8 and apply therein my softening process afterwhich the web passes over roll 36, vibrator 31 and roll 38 and issubjected to a vibrating action by the vibrator 31. After this, the webis carried from roll 38 with the abrasive side facing downwardly untilthe adhesives set up to anchor the grains after which the web may bepassed to conventional sandpaper drying rolls as previously describedfor Coated abrasives, Examples 1 and 2. This latter web in which thesteaming or softening process has been combined with the vibratingaction, will be found to be a remarkable improvement in regard to thesharpness of the points and edges of the grain and the tenacity withwhich the adhesive holds the grains as compared with the webs in whichonly one beater or the two beaters 33 and 31 were used without thetreatment in chamber I8. Furthermore, in most cases, the web made by thecombined treatments of the chamber I8, and the vibrators will have notonly a rougher and sharper coating, but one in which the grains havedefinitely better orientation with their long axes parallel to thedirection of the force of gravity at the time of treatment. In the caseof this grit and with the backing described, the beaters 33 and 31 whereused, are set to press against the backing to an extent that will causea one-half inch displacement of the backing at'the point of contact withthe beater from a straight line drawn between the two surfaces of theadjacent damper rolls at their points of contact with the backing. Inthis case, a suitable speed of the hexagonal vibrators 33 and 31 whereused is 3100 revolutions per minute. A suitable temperature within thetreating chamber I8 is 170 F. As in the previous examples, the quantityof steam admitted into the chamber I8 is adjusted to prevent substantialevaporation of the water solvent of the sizing glue. Wet steam may beused with good results. However, steam with a few degrees of super-heatmay be used with equally good or superior results.

The three examples given by way of illustration are typical of a widerange of grit sizes. Sometimes, I employ very heavy backings such aslaminations of 10 mil vulcanized fibre with drills cloth as a backingand coat the abrasive preferably on the cloth side. Such backings aremore often used with relatively coarse grits. In this case, I normallyset the beaters or vibrators to press against the backing with a greaterforce so that there is a displacement of about ave-@mains of an inch inthe backing at the lpoints of contact with the vibrator from a straightline drawn between the surfaces of the damper rolls adjacent thebacking. Furthermore, with such heavy backings and coatings, I

, coat of making adhesive.

and that it is advisable to use a higher temperature in the treatingchamber I8 and usually employ temperatures of the order of 200 F.

'I'his invention has been illustrated with particular reference to gluebond coated abrasives where it has always been a problem to prevent lossof orientation of the grains due to the softening of the making coat ofadhesive by the sizing coat of adhesive. However, my process andapparatus are not limited to use with glutinous adhesives, but may beused with a wide variety of adhesives, where the making coat of adhesiveis of a nature or in a condition in which it is substantially softenedby the sizing coat of adhesive whereby the grains are not sufficientlyanchored shortly after or during the sizing operation to preventmovement of the grains. For example, in the copending application ofNicholas E. Oglesby, Charles F. Reilly and Victor W. Gilbert, Serial No.124,506, filed February 6, 1937, there is described a method of makingresin bonded libre combination discs in which the sizing coat ofadhesive is applied over an inoompletely cured and therefore softenableSuch a web after the sizing operation may be treated by the apparatusand process illustrated in Figures 1 and 2. That is, the web may besubjected to beaters, as illustrated, or to a softening treatment in thechamber I8 or to a combination of treatments in the chamber I8 and withtheyibrators or beaters. In applying the treatment in chamber I8 to suchwebs, I introduce through the supply line 2| into the chamber I8 vaporsof a solvent for the sizing, coat of adhesive or such vapors associatedwith soluble inert gases such as air. The sizingcoat of adhesive (phenolformaldehyde resin) described in the aforesaid application of Oglesby,Reilly and Gilbert, is softenable to a considerable extent with water,and I may, therefore, prevent case hardening of the resin by introducingsteam into the chamber I8 which may be wet steam, but in this case ispreferably steam with a few degrees of super-heat. Where phenolformaldehyde resins are used to size the coated abrasive webs and theseresins have been advanced in cure before the -sizing operation to apoint where they are not softenable by Water vapor, I may introduceinstead of water vapor, vapors of alcohol which readily soften suchphenol formaldehyde resins of advance cure. r

However, in making certain types of flexible coated abrasives, a sizingadhesive of oil modifled polyhydric alcohol polybasic acid resin isused, such resins being readily softenable by aromatic solvents such astoluene or high-dash naphtha, and where such adhesives are used in thesizing operation, I may introduce into the treating chamber I8 thevapors of such aromatic solvents.

In using the various types of adhesives, the principle of the operationof the chamber I8 is the same as has been previously described withspecic reference to glutinous adhesives. In other words, the chamber I8is controlled as to temperature and partial pressure of the softeningvapors to bring about and/or maintain in the chamber a fluid and mobilecondition of the sizing coat of adhesive without case hardening of thesame whereby a superior bond is formed between the adhesive and theabrasive grains and whereby the edges and points of the abrasive grainsare remarkably free from adhesive due to the movement of the adhesiveaway from the a firm union not only with the grains, but also 'K withthe making coat of adhesive.

As illustrative of a synthetic resin that may be used in carrying out myprocess I will describe.

in detail a suitable phenol-formaldehyde resin and its application andtreatment in the process.

A suitable phenol-formaldehyde resin which may be used in making anumber of coated abrasive articles may be prepared byreacting underreflux in a jacketed container fitted with thermostatic controls and amechanical agitator, 100 parts of phenol to 82 parts 37% formalin in thepresence of an alkaline catalyst, for example, 0.8 to 1.0 part of sodiumhydroxide. The manufacture of the `resin is carried out by the usualpractice of the resin art. When the reaction has proceeded to therequired point as deter mined by the usual control tests, the watercontent of the resin as determined by the Karl Fisher reagent is reducedunder vacuum to approximately 10%. After this reduction in the watercontent, the density of the resin should be about 1.2 at C. andthe watertolerance of the resin should be approximately ccs. per 10 grams ofresin previously thinned with 10 grams of methanol. The viscosity of theresin should beabout 18 poises at 25v C. The pH of the resin should beabout 8.7 to 9. `This resin may be thinned'with water-to produce lowerviscosities whererequired or desirable in the coating and sizingoperations that areV carried outin the manufacture of the coatedabrasives. Likewise, in instances' where a higher viscosity isdesirable, a greater amount of water may be removed. in the vacuumtreatment previously referred to.

Coated abrasive, Example 4 This is what is generally known as arelatively coarse` grit coated upon a heavy backing. A suitable backingfor this example is .30 mil Vulcanized fibre. A suitable grit is No. 36fused aluminum oxide abrasive such as is sold under the trade nameAlundum." A suitable making coat of adhesive is the phenol-formaldehyderesin containing 10% of water, the preparation of which has beendescribed in detail. A suitable temperature for the application of themaking coat of adhesive is 120 F. A suitable sizing solution of adhesivefor this grit is the same phenol-formaldehyde resin previously describedcontaining 10% water. While the resin in this condition serves mypurpose well, I may also thin the resin to any extent desired by addingthereto, water. A suitable sizing temperature in this example is 130 F.As in former examples of making coated abrasives, a suitable weight ofabrasive grains may be coated onto the backing by using the making coatof adhesive described and the established methods of the art. In makingthis grit I coat onto the adhesively coated backing about lbs. persandpaper ream of the No. 36 fused aluminum oxide abrasive grains, afterwhich the abrasively coated web is' subjected to drying conditions topartially cure the making coat of adhesive. A suitable drying cycle formy purpose is one hour at '100 F., one hour at 105 F., one hour at 110one hour at O F., one hour at 120 F., one hour at F., one hour at 130F., one hour at F., one hour at 140 F., one hour at 145 F., and one hourat F. After this curing cycle, the making coatJ is still readilysoftenable by the sizing coat hereafter applied. After the curing 1, theabrasively coated web is passed from the festocns over idler rolls I2,preferably rubber F. in the glue box I5 is applied over the abrasivegrains in substantially the usual quantity in commercial practice. Fromthe calender rolls Il the sized abrasive web I0 is quickly turned aboutidler rolls I6 and I1 to face the abrasive side downwardly, and with theabrasive facing downwardly the web is led through the treating chamberI8, entering the chamber at slot I9 and leaving it at slot 20. Withinthe chamber I8 the web issubjected to atreatment with warm solventvapors. Since the resin used by way of illustration is readilysoftenable by water, I add through the supply line 2l in controlledquantities, steam, which in this case may be ordinary wet steam at 15lbs. pressure produced from steam in a line at 90 lbs. by a suitablereducing valve. While wet steam may be used, steam with a few degrees ofsuperheat is preferred. Steam is a cheap, readily available andconvenient softening vapor for addition to chamber I8. It is to beunderstood, however, that alcohol or other softening vapors may be usedinstead of steam or along with steam. Within the chamber Il, thefluidity of the sizing resin is controlled and increased as desired, butin any event, a highly fluid condition of the sizing adhesive is broughtabout and maintained within the chamber Il. Upon emerging from slot 20in the chamber I8, the web may be passed over roll 25, roll 21, roll 28and the suction drum 29, thence to the drying racks. Between theemergence of the web from the slot 20 and its turn from the controlled40 direction of travel with the abrasive side faccycle described,referring to the means of Figure 7| ing-downwardly into a verticaldirection to approach the suction drum 29, the adhesive sets to anextent that loss of orientation or dislocation of the grains, after theweb is turned from its controlled position of travel, is avoided. In

this variation of my process, the driven vibrator or whipper, such asthat illustrated by 26, has not been used but a superior result has beenobtained as compared with the coated webs of the prior art. However, apreferred method of operation includes the driven vibrator or beater 26which, in this case, may be so set against the backing of the web thatat the point of contact between the vibrator and the web, the web isdisplaced about ve-eighths of an inch from the straight line drawnbetween the bottoms of damper rolls 25 and 21. A suitable speed of thevibrator, in this case, is about 2800 revolutions per minute. The speedof the traveling web and the size of the chamber I8 in this case may beso adjusted that the web is within the chamber for a period of about twoand one-half to three seconds, although longer times within the chamberare often desirable.

The temperature within the chamber and near the surface of the goods maybe approximately F. but often higher temperatures are preferred,especially where superheated steami's used. Furthermore, the time oftravel with the abrasive facing downwardly after emergence from thechamber I8 is, in this case, not less than about eight seconds but oftenlonger times are preferred.

The treated web is passed from suction drum 29 of Figure l over idlerrolls 30 and thence to a commercial sandpaper drying room where thegoods are festooned and heated to cure the resin according to the usualmeans. Good practice is toi cure the goods in festoon form to a pointwhere the grains are well anchored in place but at the same time notcure the goods to a point where they cannot be readily removed from thecuring racks for final curing at high temperatures in either roll formor sheet form according to present known methods.

Discs so made by the special methods illustrated, referred to in Fig. 1,are found to be rougher and sharper than goods made similarly but inwhich the novel methods disclosed herein are not employed.

Coated abrasive, Example 4, has been given as a concrete illustration ofthe use of synthetic resins in my new processes. It is to -be understoodthat other resins may be used and that the means of Figure 2 may beemployed in carrying out the processes. Furthermore, reasonablemodifications of all of the means shown in Figures 1 and 2 and describedherein are contemplated.

Figures 1 and 2 illustrate the application of my process and apparatusto' coated abrasive machines now current inthe industry. Instead ofsizing the web'and then turning it so that the abrasive side facesdownwardly, I may provide an arrangement of the sandpaper equipment, asfor instance, in which the making machines and the drying festoonsbetween making and sizing are on an upper floor and the sizing machineis on a lower floor. In such a case, the web may be removed from thefestoons as shown in Figures l and 2, carried downwardly through thefloor and turned so that the abrasive side faces downwardly before thesizing operation. In this case, the sizing operation may be carried outwith the abrasive facing downwardly after which any of my treatments maybe applied such as those of chamber i8 of Figures 1 and 2 and the 1various vibrator or beater treatments, while the web is travelling withthe abrasive side facing downwardly. After the treatments, the web iscontinued along a path with the abrasive side facing downwardly until'the adhesive sets up suinciently to anchor the grains after which theweb may be moved by any convenient means to a dry. ing room if the webhas not been sufficiently dried while travelling with the abrasive sidefacing downwardly.

While I have illustrated the web passing through the chambers i8 inFigures 1 and 2, horizontally in a slightly inclined direction tothenormal, it is to be understood that the web may be traveled through thesaid chambers-horizontally in a direction perpendicular to the normal.Likewise, as the Web issues from the chambers i8, it may travel in aninclined direction-or in a horizontal direction perpendicular to thenormal.

I claim: 1

1. A coated abrasive comprising a backing, a coating of abrasive grainsheld to said backing by an adhesive making coat, the majority of saidabrasive grains being oriented with their long axes substantially atright angles to the plane of the backing, a sizing coat of adhesiveapplied over said grains, the oriented abrasive grains within thecoating having a random spacingof their ends adjacent the backing andaway from the backing but within the making coat of adhesive and having,as a result thereof, their exposed ends extending a correspondinglyvariable distance above the average level of the said sizing adhesive,the exposed points and edges of the abrasive lgrains being free from anydeleterious quantity of said sizing adhesive and the exposed ends of thegrainsin the top of the coat being spaced far apart and open.

2. A coated abrasive comprising a backing, a coating 0f abrasive grainsheld to said backing by an adhesive making coat, said coating of grains,as initially applied, consisting of a single layer of grains one graindeep and substantially all of the grains being oriented, as initiallyapplied, with their long axes substantially at right angles to the planeof the backing, a sizing coat of adhesive applied over said grains, theabrasive grains within the final coated abrasive being oriented withsubstantially all of their long axes substantially perpendicular to theplane of the backing, but having a random spacing of their ends adjacentthe backing and away from the backing but within the making coat ofadhesive and having, as a result thereof, their exposed ends extending acorrespondingly variable distance above the average level of the saidsizing ,adhesive, the exposed points and edges of the abrasive grainsbeing free from any deleterious quantity of said sizing adhesive and theexposed ends of the grains in the top of the coat being spaced far apartand open,

3. The method of making coated abrasives comprising applying a'makingcoat of adhesive to a backing, applying a layer of abrasive grains uponsaid making coat, at least a substantial lproportion of said grains asinitially applied having their long axes substantially normal to theplane of the backing, at least partially setting the making coat -toanchor the grains to the backing, applying a sizing coat of adhesiveover said grains while the said making coat is in such a state that'itis softenable by said sizing coat, and quickly after sizing, prior tosubstantial loss of said orientation of grains, maintaining the backingso coated and sized with its abrasive surface facing downwardly whilepermitting the sizing coat to soften the making coat and while settingthe adhesive at least sumciently to prevent substantial movement of thegrains within the adhesive when the coated backing ismoved so that theabrasive surface no longer faces downwardly in subsequent operationswhereby to pro-l duce a nal sized coated abrasive in which a substantialproportion of the grains have their long axes substantially normal tothe plane of the backing.

4. The :method of making coated abrasives comprising applying a makingcoat of adhesive to a backing, applying a layer of abrasive grains inoriented relationship upon said making coat whereby a substantialproportion of the grains have their long axes substantially at rightangles to the plane ofthe backing, at least partially setting saidmaking coat to anchor the grains to the backing, applying a sizing coatof adhesive over said grains while said making coat is in such acondition that it may be softened by said sizing coat, vibrating thebacking while the sizing coat is still iiuid and the making coat isbeing softened by said sizing coat whereby to prevent the abrasivegrains from losing said orientation with their long axes perpendiculart0 the backing, facing the abrasive surface downwardly, and while thecoated backing is in such position uidizing the sizing coat, softeningthe making coat and vibrating the coated backing while the 'said sizingcoat and making coat are in such a condition, and setting the adhesiveat least su'iciently hesive when the coated backing is subsequentlydisposed in other positions whereby to produce a coated abrasive productin which a substantial' proportion of the grains have their long axessubstantially normal to the backing, their exposed ends extending avariable distance above thel average level of the said sizing adhesiveand their exposed points and edges free from any deleterious quantity ofsaid sizing adhesive.

5. The method of making coated abrasives comprising applying a makingcoat of adhesive to a backing, applying a layer of abrasive grains inoriented relationship upon said making coat whereby a majority of thegrains have their long axes substantially at right angles to the planeofthe backing, at least partially setting the making coatto anchor thegrains to the backing, applying a sizing coat of adhesive over saidgrains while the making coat is in such a state that it is softenable bysaid sizing coat and quickly after sizing, prior to substantial loss ofsaid orientation, maintaining the backing so coated with its abrasivesurface facing downwardly while setting the adhesiveat least suincientlyto prevent movement of the grains within the adhesive from theirinitially applied'positions when the coated backing is moved so that theabrasive surface no longer faces downwardly in subsequentoperations-whereby to produce a final sized coated abrasive in which amajority of the grains have their long .axes substantially normal to thebacking.

6. The method of making coated abrasives comprising applying a makingcoat of adhesive to a backing, applying a layer of abrasive grains inoriented relationship upon said making coat whereby a majority of thegrains have their long axes substantially at right angles to the planeof the backing, at least partially setting the making coat to anchor thegrains to the backing, applying a sizing coat of adhesive over saidgrains while the making coat is in such a state that it is softenable bysaid sizing coat, disposing the backing so coated and sized with itsabrasive surface facing downwardly before substantial loss of saidorientation of grains has occurredl and while the backing is in suchposition uidizing the sizing coat, softening the making coat andvibrating the said coated and sized backing and, subsequently, while thecoated backing stili has its abrasive surface facing downwardly. settingthe adhesive at least sufficiently to prevent substantial movement ofthe crains within the` adhesive when the coated abrasive is moved sothat the abrasive surface no longer faces downwardly in subsequentoperations whereby to produce a final sized coated abrasive product inwhich a majority of the grains have their loner axes substantiallynormal to the backingA the-'r exposed ends extending a variable distanceabove the average level of the said sizing adhesive and their exposedpoints and edges free fromA any deleterious quantity of said sizingadhesiveA 7. The method of making coated abrasives cornprising applyinga making coat of adhesive to a backing. applying a layer of abrasivegrains upon said making coat. a substantial proportion nf said grainshaving their long axes substantially at right angles to the plane of thebackinf.1 at least partially .setting the making coat to anchor thegrains to the backing. anplving a sizing coat of adhesive over saidgrains whilev the making coat is in such a state that it is softenablebv said sizing coat, disposing the backing so coated and sized with itsabrasive surface facing downwardly before substantial loss of saidorientation of grains has occurred and while the backing is in suchposition iluidizing the sizing coat, softening the making coat andvibrating the said coated and sized backing and, subsequently, while thecoated backing still has its abrasive surface facing downwardly, settingtheadhesive at least sufilciently to prevent substantial movement of thegrains within the adhesive when the coated abrasive is moved so that theabrasive surface no longer faces downwardly in subsequent operationswhereby to produce a final sized coated abrasive product in which amajority of the grains have their long axes substantially normal to thebacking, their exposed ends extending a variable distance above theaverage level of the said sizing adhesive and their exposed points andedges free from any deleterious quantity of said sizing adhesive. Y 8.The method of making coated abrasives comprising applying a making coatof adhesive to a backing, applying a layer of abrasive grains upon saidmaking coat, at least a substantial proportion of said grains asinitially applied having their long axes substantially normal to theplane of the backing. at least partially setting the making coat toanchor the grains to the backing,` applying a sizing coat of adhesiveover said grains while the making coat is in such a state that it issoftenable by said sizing coat, and prior to substantial loss of saidorientation of grains maintaining the backing so coated with itsabrasive surface facing downwardly while fluidizing the sizing coat,and, subsequently, While the abrasive coated surface of the backing isstill facing downwardly, setting the adhesive at least sufficiently toprevent movement of the grains within the adhesive when the coatedbacking is moved so that the abrasive surface no longer faces downwardlyin subsequent operations whereby to produce a final sized coatedabrasive in which a substantial proportion of the grains have their longaxes substantially normal to the backing and the exposed points andedges of thegrain are free from any deleterious quantity of said sizingadhesive.

9. The method of making coated abrasives comprising applying a makingcoatof adhesive to a backing, applying a layer of abrasive grains vuponsaid making coat, at least a substantial proportion of said grains asinitially applied having their long axes substantially normal to theplane of the backing, at least partially setting the making coat toanchor the grains to the backing, applying a sizing coat of adhesiveover said grains while the making coat is in such a state that it issoftenable by said sizing coat, at some stage while the sizing coat isfluid and the making vcoat is softened, vibrating the backing so coatedand sized by a vibrating force applied to the non-abrasive side of thebacking effective to maintain or improve the orientation of said grains.and maintaining the backing so coated with its abrasive surface facingdownwardly while setting' the adhesive at least sufficiently to preventsubstantial movement of the grains within the adhesive when the saidcoated and sized backing is moved so that the abrasive surface no longerfaces downwardly in subsequent operations, whereby to produce a flnalsized coated abrasive in which a substantial proportion of the grainshave their long axes substantially normal to the plane of the backing.

10. The method of making coated abrasives comprising applying a makingcoat of adhesive m a backing, applying a layer of abrasive grains uponsaid making coat, at least a substantial proportion of said grains asinitially applied having their long axes substantially normal to theplane of the backing, at least partially setting the making coat toanchor the grains to the backing, `applying a sizing coat of adhesiveover said grains while the making coat is in such a state that it issoftenable by said sizing coat, and prior to substantial loss of saidorientation of grains maintaining the backing so coated with itsabrasive surface facing downwardly while subjecting its abrasivelycoated side to a solventbearing atmosphere effective to fluidize thesizing coat and subsequently while the abrasive surface is still facingdownwardly, setting the adhesive at least suiciently to preventsubstantial movement of the grain within the adhesive when the saidcoated am?l sized backing is moved so that the abrasive surface nolonger faces downwardly in subsequent operations, whereby to produce afinal sized coated abrasive in which a substantial proportion of thegrains have their long axes substantially normal to the plane of thebacking and the exposed points and edges of the grains are free from anydeleterious quantity of said sizing adhesive. v

11. The method of making coated abrasives comprising applying a; makingcoat of adhesive to a backing, applying a layer of abrasive grains uponsaid making coat, at least a substantial proportion of said grains asinitially applied having their long axes substantially normal to theplane of the backing, at least partially-I setting the making coat toanchor the grains to the backing, applying a sizing coat of adhesiveover said grains while the making coat is in such a state that it issoftenable by said sizing coat, vibrating the backing so coated by avibrating force applied to the non-abrasive side of the backing which iseiective to maintain or improve said orientation of said grains, andprior to substantial loss of said orientation of grains maintaining thebacking so coated and sized with its abrasive surface facing downwardlywhile setting the adhesive at least sufficiently to prevent substantialmovement of the grains within the adhesive when the coated and sizedbacking is moved so that the abrasive surface no longer faces downwardlyin subsequent operations, whereby to produce a nal sized coated abrasivein which a substantial proportion of the grains have their long axessubstantially normal to the plane of the backing.

NICHOLAS E. OGLESBY.

